'\" e
'\"! eqn | mmdoc
'\"macro stdmacro
.ds Vn Version 1.2
.ds Dt 6 March 1997
.ds Re Release 1.2.0
.ds Dp May 02 11:53
.ds Dm 37 build2dmi
.ds Xs 21901 10 build2dmipmaps.gl
.TH GLUBUILD2DMIPMAPS 3G
.SH NAME
.B "gluBuild2DMipmaps
\- builds a two-dimensional mipmap

.SH C SPECIFICATION
GLint \f3gluBuild2DMipmaps\fP(
GLenum \fItarget\fP,
.nf
.ta \w'\f3GLint \fPgluBuild2DMipmaps( 'u
	GLint \fIinternalFormat\fP,
	GLsizei \fIwidth\fP,
	GLsizei \fIheight\fP,
	GLenum \fIformat\fP,
	GLenum \fItype\fP,
	const void \fI*data\fP )
.fi

.EQ
delim $$
.EN
.SH PARAMETERS
.TP \w'\fIinternalFormat\fP\ \ 'u 
\f2target\fP
Specifies the target texture.  Must be \%\f3GL_TEXTURE_2D\fP.
.TP
\f2internalFormat\fP
Requests the internal storage  of the texture image.  The most
current version of the SGI implementation of GLU does not check this
value for validity before passing it on to the underlying OpenGL
implementation.  A value that is not accepted by the OpenGL
implementation will lead to an OpenGL error.  The benefit of not
checking this value at the GLU level is that OpenGL extensions can add
new internal texture formats without requiring a revision of the GLU
implementation.  Older implementations of GLU check this value and
raise a GLU error if it is not 1, 2, 3, or 4 or one of the following
symbolic constants:
\%\f3GL_ALPHA\fP,
\%\f3GL_ALPHA4\fP,
\%\f3GL_ALPHA8\fP,
\%\f3GL_ALPHA12\fP,
\%\f3GL_ALPHA16\fP,
\%\f3GL_LUMINANCE\fP,
\%\f3GL_LUMINANCE4\fP,
\%\f3GL_LUMINANCE8\fP,
\%\f3GL_LUMINANCE12\fP,
\%\f3GL_LUMINANCE16\fP,
\%\f3GL_LUMINANCE_ALPHA\fP,
\%\f3GL_LUMINANCE4_ALPHA4\fP,
\%\f3GL_LUMINANCE6_ALPHA2\fP,
\%\f3GL_LUMINANCE8_ALPHA8\fP,
\%\f3GL_LUMINANCE12_ALPHA4\fP,
\%\f3GL_LUMINANCE12_ALPHA12\fP,
\%\f3GL_LUMINANCE16_ALPHA16\fP,
\%\f3GL_INTENSITY\fP,
\%\f3GL_INTENSITY4\fP,
\%\f3GL_INTENSITY8\fP,
\%\f3GL_INTENSITY12\fP,
\%\f3GL_INTENSITY16\fP,
\%\f3GL_RGB\fP,
\%\f3GL_R3_G3_B2\fP,
\%\f3GL_RGB4\fP,
\%\f3GL_RGB5\fP,
\%\f3GL_RGB8\fP,
\%\f3GL_RGB10\fP,
\%\f3GL_RGB12\fP,
\%\f3GL_RGB16\fP,
\%\f3GL_RGBA\fP,
\%\f3GL_RGBA2\fP,
\%\f3GL_RGBA4\fP,
\%\f3GL_RGB5_A1\fP,
\%\f3GL_RGBA8\fP,
\%\f3GL_RGB10_A2\fP,
\%\f3GL_RGBA12\fP or
\%\f3GL_RGBA16\fP.
.TP
\f2width\fP, \f2height\fP
Specifies in pixels the width and height, respectively, of the texture image. 
.TP
\f2format\fP
Specifies the  of the pixel data.
Must be one of
\%\f3GL_COLOR_INDEX\fP,
\%\f3GL_DEPTH_COMPONENT\fP,
\%\f3GL_RED\fP,
\%\f3GL_GREEN\fP,
\%\f3GL_BLUE\fP,
\%\f3GL_ALPHA\fP,
\%\f3GL_RGB\fP,
\%\f3GL_RGBA\fP,
\%\f3GL_BGR\fP,
\%\f3GL_BGRA\fP,
\%\f3GL_LUMINANCE\fP, or
\%\f3GL_LUMINANCE_ALPHA\fP.
.TP
\f2type\fP
Specifies the data type for \f2data\fP.
Must be one of
\%\f3GL_UNSIGNED_BYTE\fP,
\%\f3GL_BYTE\fP,
\%\f3GL_BITMAP\fP,
\%\f3GL_UNSIGNED_SHORT\fP,
\%\f3GL_SHORT\fP,
\%\f3GL_UNSIGNED_INT\fP,
\%\f3GL_INT\fP, 
\%\f3GL_FLOAT\fP, 
\%\f3GL_UNSIGNED_BYTE_3_3_2\fP,
\%\f3GL_UNSIGNED_BYTE_2_3_3_REV\fP,
\%\f3GL_UNSIGNED_SHORT_5_6_5\fP,
\%\f3GL_UNSIGNED_SHORT_5_6_5_REV\fP,
\%\f3GL_UNSIGNED_SHORT_4_4_4_4\fP,
\%\f3GL_UNSIGNED_SHORT_4_4_4_4_REV\fP,
\%\f3GL_UNSIGNED_SHORT_5_5_5_1\fP,
\%\f3GL_UNSIGNED_SHORT_1_5_5_5_REV\fP,
\%\f3GL_UNSIGNED_INT_8_8_8_8\fP,
\%\f3GL_UNSIGNED_INT_8_8_8_8_REV\fP,
\%\f3GL_UNSIGNED_INT_10_10_10_2\fP, or
\%\f3GL_UNSIGNED_INT_2_10_10_10_REV\fP.
.TP
\f2data\fP
Specifies a pointer to the image data in memory.


.SH DESCRIPTION
\%\f3gluBuild2DMipmaps\fP builds a series of prefiltered two-dimensional texture maps of decreasing
resolutions called a mipmap. This is used for the antialiasing of
texture-mapped primitives.
.P
A return value of zero indicates success, otherwise a GLU error code is
returned (see \%\f3gluErrorString\fP).
.P
Initially, the \f2width\fP and \f2height\fP of \f2data\fP are checked to see if they
are a power of 2. If not, a copy of \f2data\fP (not \f2data\fP), is scaled up
or down to the nearest power of 2. This copy will be used for subsequent
mipmapping operations described below. (If \f2width\fP or \f2height\fP is exactly
between powers of 2, then the copy of \f2data\fP will scale upwards.)  For
example, if \f2width\fP is 57 and \f2height\fP is 23 then a copy of \f2data\fP will
scale up to 64 in \f2width\fP and down to 16 in depth, before mipmapping takes
place.
.P
Then, proxy textures (see \f3glTexImage2D\fP) are used to determine if
the implementation can fit the requested texture. If not, both dimensions
are continually halved until it fits. (If the OpenGL version is \(<= 1.0,
both maximum texture dimensions are clamped to the value returned
by \f3glGetIntegerv\fP with the argument \%\f3GL_MAX_TEXTURE_SIZE\fP.)
.P
Next, a series of mipmap levels is built by decimating a copy of \f2data\fP
in half along both dimensions until size $1 ~times~ 1$ is reached. At
each level,
each texel in the halved mipmap level is an average of the corresponding
four texels in the larger mipmap level. (In the case of rectangular
images, the decimation will ultimately reach an $N ~times~ 1$ or
$1 ~times~ N$ configuration. Here, two texels are averaged instead.)
.P
\f3glTexImage2D\fP is called to load each of these mipmap levels.
Level 0 is a copy of \f2data\fP.  The highest level is
${log sub 2} ( max ("width","height"))$.  For example,
if \f2width\fP is 64 and \f2height\fP is 16
and the implementation can store a texture of this size, the following
mipmap levels are built: $64 ~times~ 16$, $32 ~times~ 8$, $16 ~times~ 4$,
$8 ~times~ 2$, $4 ~times~ 1$, $2 ~times~ 1$ and $1 ~times~ 1$. These correspond to
levels 0 through 6, respectively.
.P
See the \f3glTexImage1D\fP reference page for a description of the
acceptable values for \f2format\fP parameter. See the \f3glDrawPixels\fP 
reference page for a description of the acceptable values 
for \f2type\fP parameter.
.SH NOTES

Note that there is no direct way of querying the maximum level. This can
be derived indirectly via \f3glGetTexLevelParameter\fP. First, query
for the width and height actually used at level 0.  (The width and
height may not be equal to \f2width\fP and \f2height\fP respectively since proxy
textures might have scaled them to fit the implementation.)  Then the
maximum level can be derived from the formula
${log sub 2}( max (\f2width\fP,\f2height\fP))$.
.SH NOTES
Formats \%\f3GL_BGR\fP, and \%\f3GL_BGRA\fP, and types 
\%\f3GL_UNSIGNED_BYTE_3_3_2\fP,
\%\f3GL_UNSIGNED_BYTE_2_3_3_REV\fP,
\%\f3GL_UNSIGNED_SHORT_5_6_5\fP,
\%\f3GL_UNSIGNED_SHORT_5_6_5_REV\fP,
\%\f3GL_UNSIGNED_SHORT_4_4_4_4\fP,
\%\f3GL_UNSIGNED_SHORT_4_4_4_4_REV\fP,
\%\f3GL_UNSIGNED_SHORT_5_5_5_1\fP,
\%\f3GL_UNSIGNED_SHORT_1_5_5_5_REV\fP,
\%\f3GL_UNSIGNED_INT_8_8_8_8\fP,
\%\f3GL_UNSIGNED_INT_8_8_8_8_REV\fP,
\%\f3GL_UNSIGNED_INT_10_10_10_2\fP, and
\%\f3GL_UNSIGNED_INT_2_10_10_10_REV\fP are only available if the GL version 
is 1.2 or greater and if the GLU version is 1.3 or greater.
.SH ERRORS
\%\f3GLU_INVALID_VALUE\fP is returned if \f2width\fP, or \f2height\fP is < 1.
.P
\%\f3GLU_INVALID_ENUM\fP is returned if \f2internalFormat\fP, \f2format\fP, or \f2type\fP is not 
legal.
.P
\%\f3GLU_INVALID_OPERATION\fP is returned if \f2type\fP is \%\f3GL_UNSIGNED_BYTE_3_3_2\fP or \%\f3GL_UNSIGNED_BYTE_2_3_3_REV\fP
and \f2format\fP is not \%\f3GL_RGB\fP.
.P
\%\f3GLU_INVALID_OPERATION\fP is returned if \f2type\fP is \%\f3GL_UNSIGNED_SHORT_5_6_5\fP or \%\f3GL_UNSIGNED_SHORT_5_6_5_REV\fP
and \f2format\fP is not \%\f3GL_RGB\fP.
.P
\%\f3GLU_INVALID_OPERATION\fP is returned if \f2type\fP is \%\f3GL_UNSIGNED_SHORT_4_4_4_4\fP or \%\f3GL_UNSIGNED_SHORT_4_4_4_4_REV\fP
and \f2format\fP is neither \%\f3GL_RGBA\fP nor \%\f3GL_BGRA\fP.
.P
\%\f3GLU_INVALID_OPERATION\fP is returned if \f2type\fP is \%\f3GL_UNSIGNED_SHORT_5_5_5_1\fP or \%\f3GL_UNSIGNED_SHORT_1_5_5_5_REV\fP
and \f2format\fP is neither \%\f3GL_RGBA\fP nor \%\f3GL_BGRA\fP.
.P
\%\f3GLU_INVALID_OPERATION\fP is returned if \f2type\fP is \%\f3GL_UNSIGNED_INT_8_8_8_8\fP or \%\f3GL_UNSIGNED_INT_8_8_8_8_REV\fP
and \f2format\fP is neither \%\f3GL_RGBA\fP nor \%\f3GL_BGRA\fP.
.P
\%\f3GLU_INVALID_OPERATION\fP is returned if \f2type\fP is \%\f3GL_UNSIGNED_INT_10_10_10_2\fP or \%\f3GL_UNSIGNED_INT_2_10_10_10_REV\fP
and \f2format\fP is neither \%\f3GL_RGBA\fP nor \%\f3GL_BGRA\fP.
.SH SEE ALSO
\f3glDrawPixels(3G)\fP,
\f3glTexImage1D(3G)\fP,
\f3glTexImage2D(3G)\fP, 
\f3glTexImage3D(3G)\fP,
\%\f3gluBuild1DMipmaps(3G)\fP,
\%\f3gluBuild3DMipmaps(3G)\fP,
\%\f3gluErrorString(3G)\fP, 
\f3glGetTexImage(3G)\fP,
\f3glGetTexLevelParameter(3G)\fP,
\%\f3gluBuild1DMipmapLevels(3G)\fP,
\%\f3gluBuild2DMipmapLevels(3G)\fP,
\%\f3gluBuild3DMipmapLevels(3G)\fP
